1. Chapter 10: Cell Growth and Division
Growth , Development and Reproduction

2. 10.1: Cell Growth, Division and Reproduction
WHY DO CELLS DIVIDE???
To reproduce.
To grow bigger.
To repair injuries.
To become more efficient.

3. A. Limits of Cell Growth Volume grows faster than surface area
Therefore a larger cell has a more difficult time getting stuff into (oxygen & nutrients) and out of (wastes) the cell
SOLUTION: Cell Division

4. B. Rates of Cell Growth Vary depending on cell type
E. Coli every 30 minutes
Some cells take much longer to divide or “stop” dividing for a while
Prokaryotic Cell Division
Binary Fission – asexual

5. Section 10.2 Chromosomes Chromosomes: “colored body”
seen only when the cell divides
contain genetic info in the form of DNA
are coiled chromatin
Composition of Chromatin
Make up chromosomes
Composed of DNA and protein called histones (helps to condense the DNA)
DNA in a chromosome is 10,000x longer than the chromosome itself
Nucleosome: DNA coiled around histones (“ball with string”)
Nucleosomes coil into supercoils – then into chromosomes
Must condense in order to separate correctly during mitosis

6. Chromosome Structure Can only see chromosomes during division
Each chromosome replicates and is paired as sister chromatids joined at a centromere
Human cell = 46 chromosomes (2n)
“n” number = 23 = “haploid”
2n = 46 = “diploid”
4n = 92 (during interphase)
Body cells (aka somatic cells) = 2n = MITOSIS
Sex cells (aka eggs & sperm) = n = MEIOSIS

7. 10.2 Cell Division: Mitosis & Cytokinesis
Define mitosis and cytokinesis.
Describe the cell cycle and the changes that take place during interphase.
Discuss the events and significance of mitosis.

8. The Process of Cell Division
Growth, prepares for division, divides (anywhere from 6 hours to 100 days)
The CELL CYCLE
3 Parts
Interphase
Mitosis (PMAT)
- few minutes to several days
Cytokinesis

9. 1. Interphase – 3 stages
More than 90% of the life of a cell is spent in this phase
G1: cell growth, development, and protein production (longest)
S: “Synthesis”, DNA replication
G2: Organelles replicated (shortest)
Note: DNA exists as chromatin (no chromosomes yet)

10. Two main stages of cell division:
Mitosis: nucleus divides, produces 2 nuclei identical to parent cell and each other
Cytokinesis: cytoplasm divides, produces 2 cells

11. 2. Mitosis - Prophase
Longest phase of MITOSIS (50-60 % of total time required for mitosis)
Nuclear membrane starts to disintegrate
Chromosomes condense (become visible) – seen as 2 identical chromatids lying side by side held together by centromeres
Centrioles move to opposite poles
Spindle fibers grow from centrioles, attach at centromeres

12. 3. Mitosis – Metaphase (hint “M”=middle)
Chromosomes attach to the spindle fibers
Chromosomes line up in the middle (aka equator)
Spindle fibers run from centrosomes to centromeres of the chromosomes

13. 4. Mitosis - Anaphase (hint “A” = away)
Centromeres split
Spindles retract and pull sister chromatids apart
Chromosomes move to opposite poles (toward centrioles)

14. 5. Mitosis - Telophase Chromosomes cluster at poles
Chromosomes uncoil – back into chromatin
Nuclear envelope reforms around each new nuclei
Mitosis is done
Cell membrane begins to pinch in the middle

15. 6. Cytokinesis
Cell membrane moves inward and pinches in the middle forming two identical cells
In plant cells – a cell plate (eventually becomes the cell wall) and cell membrane appear separating the 2 new cells
There are now 2 identical cells – same DNA, etc.

17. Mitosis Animations

18. Mitosis: AP Text Animation AP Bioflix - Mitosis Bozeman - Mitosis McGraw Hill - Simple Mitosis Summary
Mitosis Song
Scene from Twilight
Meiosis: Meiosis Squaredance (Long) AP Text Animation AP Bioflix - Meiosis Bozeman - Meiosis Bozeman - Mitosis vs. Meiosis Bozeman - Mitosis vs. Meiosis Simulation

19. 10.3 Controls on Cell Growth
Some cells rarely/never divide – nervous and heart cells
Some cells divide daily – skin and digestive tract cells
STOP switch: cells stop growing when they bump into each other
ON switch: cut or break in tissue cause cells to grow rapidly (but growth slows as healing reaches completion)

20. Regulating the Cell Cycle
Cyclins – proteins that regulate the timing of the cell cycle in eukaryotic cells by
Regulatory Proteins
Internal Regulators – respond to event occurring inside the cell (proceed only when certain checkpoints have been cleared)
External Regulators – respond to events outside the cell – direct cells to speed up or slow down the cell cycle (embryonic development and wound healing
Apoptosis – Programmed Cell Death
When not occurring when needed, many disease can result (cancer, AIDS, Parkinson’s)

21. D. Uncontrolled Cell Growth
= CANCER
Cells have lost the ability to control their own rate of growth
Continue to divide until nutrient supply is exhausted (may invade other normal cell’s space, even if they bump into each other, and use up their nutrients)

22. Cancer Tumor – mass of cells NOT responding to “stop” signals Causes
Benign – does not spread to healthy surrounding tissue
Malignant – cancerous tumors which spread to and destroy healthy surround tissue
Metastasis – spreading
Causes
Genetic Defects
Can be caused by lots of different factors (smoking, TANNING, radiation exposure, viral infections, defective genes…)
Treatment Options …

23. 10.4 Cell Differentiation
Differentiation – process by which cells become specialized and differentiate into many different types of cells
Stem Cells – cells that are totipotent (able to develop into any type of cell in the body – fertilized egg and cells produced by first few cell divisions)
Embryonic stem cells are considered pluripotent b/c they produce the cells in the early embryo, can develop into many different types, but not all types of cells
Adult stem cells are considered multipotent b/c they can develop into many different types of differentiated cells (bone marrow cells can make different types of blood cells, brain cells make neurons or nerve cells)

24. Pop Quiz???? What is the main goal of cell division?
What are the 3 phases of interphase?
What are the 4 phases of mitosis?
A cell has 12 chromosomes. At the end of cell division how many cells will there be?
A cell has 12 chromosomes. At the end of cell division how many chromosomes will there be in each cell?